And sorry, I sometimes forget the obvious. With only two layers of paint your fastest stripping method may be scrapers with really sharp blades. If you can get it off this way you also avoid the heat generated from chemical, abrasive, infrared, etc. stripping methods that can melt paint into the grain of soft woods like pine.
If the pine was painted the way it should be with a good primer, and especially one sealing and penetrating, you will have trouble getting it out of the grain. Try stripping it down though. Then shellac. Then strip the shellac and see if it pulls pigment in the grain out.